Pleasanton, city (1990 pop. 50,553), Alameda co., W Calif., a suburb of the San Francisco–Oakland area, in a vineyard and dairy region; inc. 1894. Wine and cheese are produced, and there are publishing and stone-quarrying industries. Manufactures include electronic, computer, and transportation equipment; primary metals; and medical supplies. Pleasanton experienced strong population growth in the late 20th cent.